Curved tooth gear and pinion wheels



July 8, 1941. F. H. BooR 2,248,158

CURVED TOOTH GEAR AND PINIONY WHEELS y 2 Shee'f-.s-Sheet 1 Filed Dec. 20, 1939 INVENTR. y FRANCIS H. 500E July 8, 1.941.

F. H. BOOR CURVED TOOTH GEAR AND PINION WHEELS Filed Dec. 20, 1939 2 Sheets-:Sheetl 2 INVENTOR.

ATTORNEY.

Patented July 8, 1941 22d8Ji58 @TURED TOOTH GEAR AND PINION WHEELS 'Francis H. Boor, Lafayette, Ind., assignor to Fairfield Manufacturing Company Application December 20, 1939, Serial No. 310,106

(Cl. 'i4-466) d Claims. My invention relates in general to gear wheel and pinion wheel constructions and more particularly to gear wheel and pinion wheel constructions having teeth curved across the face of the wheel, and includes both curved tooth spur gearing and curved tooth helical gearing.

In the past, gears have been provided with curved teeth, but the applicants invention constitutes an improvement thereon. The present invention not only constitutes animprovement over curved tooth gearing but also gives important advantages over the straight tooth spur, the helical tooth spur, the continuous tooth herringbone and the interrupted tooth herringbone, avoiding at the same time a lot of the disadvantages.

An object of my invention is to provide a. gear wheel and pinion wheel construction arranged such that the tooth contact or engagement can be located on any transverse section of the tooth face desired; that is to say. the tooth contact or engagement may be located.' near one end or near the median plane of the wheel depending upon the particular application.

Another object of my invention is to provide for controlling t-he length of the tooth contact or engagement by mis-matching the cutter radii.

Another, object of my invention is to provide for generating the convex and the concave sides of a tooth space between adjacent teeth of the gearing about a common center, but with a different radii of curvatures.

Another object of my invention is to provide for generating the convex and the concave sides of a tooth space between acacent teeth of the gearing about a plane of the gearing, but with a different radii of curvatures.

Anotherl object of my invention is to provide for generating the convex and the concave sides of a tooth space between adjacent teeth of the gearing about a common centerl lying outside of the plane of the gearing, but having different radii of curvatures.

Another object of my invention is the provision of a 'gear wheel and pinion wheel construction arranged such that the convex side of the tooth space of one wheel and the concave side of the tooth space of the other wheel engage each other in the central transverse region of the wheel with the end of the teeth relieved to provide a rocking engagement to accommodate for limited axial mis-alignment of the wheels.

Another object of my invention'is the provision of a gear wheel and pinion wheel concommon center lyingwithin the struction arranged such that deflection under load of the supporting shafts, bearings and other component parts will not cause the tooth contact or engagement to become concentrated at one end oi the teeth.

Another object of my invention is the provision of a gear wheel and pinion wheel construction arranged such that a limited axial misalignment of the wheels may be compensated for without damage to the teeth.

Other objects and a fuller understanding of my invention may be had by referring to the following description and claims, taken in conjunction with the accompanying drawings, in which:

Figure 1 is a plan view embodying my gear wheel and pinion wheel construction, shqyving in addition by the dash-and-dot lines a limited axial mis-alignment of the wheels;

Figure 2 is a perspective and fragmentary view of a milling machine adapted to cut gear and pinion wheels in accordance with the features of my invention;

Figure 3 is a diagrammatic side view showing the relative position of a wheel blank and the path of the cutter for producing a curved tooth spur wheel in accordance with the provisions of my invention;

Figure 4 is a diagrammatic side view illustrating the relative position of a wheel blank and the path taken by the cutter in producing a curved tooth helical wheel in accordance with the features of my invention;

Figure 5 is a view illustrating the difference in in the curvature of the concave side and the convex side of a tooth space between adjacent teeth of my gearing;

Figure 6 is an enlarged view showing the alternate staggered position of the cutters about the cutting head of the milling machine;

Figure 7 is a fragmentary view of a wheel hovling the generated involute profile of the Figures 8 to 12, inclusive, are a series of progressive diagrammatic plan views illustrating the relative positions of the wheel blank and the cutter in shaping a tooth space; and' Figures 13 to 17, inclusive, are a series of progressive diagrammatic plan views showing the relative positions of a wheel blank and the cutter in finishing a side of a tooth space.

With reference to Figure 1 of the drawings, my gear wheel is indicated by the reference character 20 andmy pinion wheel is indicated by the reference character 2|, and each may be suitably secured to operating shafts 22 and 23respectively. In Figure 1, the teeth are oi `the curved tooth spur type. The concave side and the convex side of a tooth space between adjacent teeth are indicated, respectively, by the reference characters 21 and 28. The dash-and-dot line 24 in Figure 1, illustrates the manner that the gear wheel 20 and the pinion wheel 2| may become mis-aligned resulting, for example, from deiiection under load of the supporting shafts, bearings or other component parts of the machinery. As the pinion wheel and the gear wheel move from a position of perfect alignment to a position of mis-alignment, as illustrated by the dash-anddot line 24 in Figure 1, the curved teeth of the gear Wheel 20 and the curved teeth of the pinion wheel 2| make rocking transverse engagement with respect to each other and prevent the tooth load from becoming concentrated in a small area at one end of the teeth. In actual practice, many gear failures are caused by the tooth load becoming concentrated on a small area at one end of the teeth due to deliections in the housing bearings and other parts of the machinery supporting the shaft and the gearing.

My gearing may be constructed by a milling machine 29, as illustrated in Figure 2, and it may comprise generally a cutting head 3| having a plurality of peripherially arranged, alternately staggered cutters 32 and 33 arranged to revolve about a common axial center 34. The wheel blank 30 which is to be processed may be carried by a fixture 35 suitably mounted upon a reciprocating table 33 which transversely moves the wheel blank 30 with reference to the revolving cutters 32 and 33. 'Ihe wheel blank 30 is arranged to be non-rotatively secured to the upper end of a shaft which extends vertically through the fixture 35, such as for example by a nut 35.

A gear wheel 31 is non-rotatively connected to the lower end of the vertical shaft and meshes with a longitudinal and transverse rack 33. As the reciprocating table 39 movesfrom right to left, indicated by the arrow line, the wheel blank 30 is caused to rotate in a clockwise direction as viewed from above. In cutting a curved tooth spur wheel, as shown in Figure 3 where the path of the cutters 32 and 33 is indicated by the dashand-dot circle 43. the median plane 42 of the wheel blank passes through the axial center 34 of the cutitng head 3|. 'Ihis means thatvthe curved teeth of the spur type gear are symmetrical upon each side of the median plane of the wheel.

'I'he alternate cutters staggered such as shown what is termed in the art as a spread-blade cutter. By this arrangement, the cutter blades 3| cut on the one side of a tooth space and then the cutter blades 32 cut on the opposite side of the tooth space. 'I'he eiiective width of the bottom of a tooth space is represented in Figure 6 by the 32 and -33 are slightly in Figure 6, producing ing of the gear 31 with the rack 38 causes the wheel blank 33 to revolve in a clockwise direction, as viewed from above and indicated by the arrow. as the staggered blades 32 and 33 cut a tooth space in the blank 3l. 'I'he teeth which are cut in this fashion are generated with involute profiles, as illustrated by the series of diagrammatic distance W, called the point-width of the cutter.

as indicated bythe arrow in Figure 2. The meshplan views in Figures 8 to 12, inclusive. The cutter that cuts on the inside in these series of views is represented by the reference character 33 and the cutter that cuts on the outside is represented by the reference character 32. A fter each tooth space is cut, the wheel blank 30 may be indexed by withdrawing the gear 31 from the rack 33 and rotating the teeth of the gear 31 with respect to the teeth of the rack 33 a distance equal to the pitch of the teeth being cut upon the blank 30. After the indexing is established, the wheel blank 30 is again brought into engagement with the cutters as explained above for cutting the nextA tooth space. This process is continued until all of the teeth of the gear blank 30 are cut. y

Depending upon the particular application and use of the gear wheel and pinion wheel construction, the curved teeth may be cut in one operation or they may be cut in two operations; a roughing operation and a iinishing operation. In Figures 13 to 17, inclusive, I illustrate the action between the cutters and the wheel blank when finishing one side of a tooth space, after the teeth have been cut by the roughing operation as that illustrated in Figures 8 to 12, inclusive. The root diameter of the finished cut is slightly greater than the root diameter of the rough cut. Thus, for example, in Figure 7 the root diameter of the rough cut is indicated by the diameter 58 and the root diameter of the finished cut is illustrated by the diameter 53. In actual construction, the root diameter of the finished cut may be from .015 to .030 greater than the root diameter of the roughing cut. The view in Figure 7 is somewhat exaggerated. The same type of cutters are used for the finishing operation as for the roughng operation, although the finishing cutters are usually made more accurate. In Figures 13 to 17, inclusive, the reference characters 45 and 46 represent the outside and the inside iinishing cutters, respectively, of the milling machine. In these series of iigures, I show only one side of the tooth space being finished by the o utside cut ters 45, which are illustrated by the solid lines. This is generally referred to as the single-side method. The finishing cutters 45 are the onlyl cutters performing a cutting operation during the cutting of the side of the tooth illustrated in these drawings. After all the teeth have been finished on one side, the work is indexed the proper amount so that the inside cutters 43, rep-v resented by the dotted line, iinish the opposite side of each tooth space. Ihe mean radius 43 for the cutters in the roughing operation, as shown in Figures 8 to 12, inclusive, and the mean radius 49 in the finishing operation, as shown in Figures 13 to 17 inclusive, are the same. Depending upon the design of the gear wheel and pinion wheel construction, the finishing of the teeth may also be done by the spread-blade method, that is both sides of each tooth space are iinished in a single cutting cycle. In finishing the teeth by the single-side method, the point-width of the finishing cutter is less than the point-width of the roughing cutter. However, when the gearing is nished by the spread-blade method the pointwidth of the -nishing cutters are wider than the point-width of the roughing cutters. It is a customary practice to remove about .020 `stock' from curved helical gear thegenerating center 34 lies each side of the tooth during the finishing opelaoutside ,of the median plane of the gear blank. tion. depending upon the Size of the teeth beim! l' Although I have described my invention with generated. a certain degree of particularity, it is under- In my gear wheel and pinion wheel construcstood that the present disclosure has been made tion, -the convex side of the teeth or one wheel only by way of example and that numerous engage the concave side or the teeth oi the mat Y changes in the details of construction and the ing wheel. The convex side or each tooth is. combination and arrangement of parts may be generated by the inside cutting edges of the resortedtowithout departing from the spirit and cutters and the concave side of each tooth is 1o the scope ofthe invention as hereinafter claimed.

produced by the outside cutting edges of the cut- I claim as my invention;

ters. It the mean radius4 of the cutters is desig- 1. A gear wheel and a pinion wheel construcnated as MR, then -the radius travelled by the tion comprising. 'a gear wheel having an axis inside cutting edges is MR minus. and having a plurality ot curved teeth each hav- W ing a generated involute profile, the spaces be- -2- tween the teeth being the same from one side of the wheel to the other and the sides of the where W is the point-width of the cutters, and spaces being es cf eil-cies having n nommen the radius travelled by the outside cutting edges center, a pinion wheel having an axis substanis MR plus tially parallel to the axis oi! the gear wheel and W having a plurality of similar curved teeth each having a generated involute prole adapted to mesh with the curved teeth of the gear wheel, These different radii are Shown in Figure 5' the spaces between the teeth of the pinion wheel This shows how it is possible to make two matbeing the seme from one side of the wheel te ing gears With the Same outtei and generate the the other and the sides of the spaces being arcs convex side and the concave side of a tooth space ef circles having a commun cente the teeth with different radii of curvatures so that a rockspace between adjacent teeth of the gear wheel ing engagement iS Produced to oeoommodete um' and o! the pinion wheel dened by a convex and ited misallgnment 0f' the mating Wheels resulting 3o a. concave side, each said side being curved about from deiiectionS under lof"d of the Supporting the same generating center with diiierent radii Shafts, bearings o1' other oomhoheht Petto of of curvature, the radius o! curvature of the conthe machinery supporting the gearing construcvex side of the teeth space being emeiier than tion. The mis-matching of the teeth governs the the radius of curvature ci the concave Side by length of .the tooth Contact of the rocking eh' 35 an amount substantially equal to the tooth space gagement- The reason that this rocking en' between adjacent teeth, and the convex side of sagement iS S0 desirable is that helps t0 00mthe tooth space of one and the concave pensate for deflections that are always Present side of the tooth space of the other wheel enin bearings, shafts, and housings when under gaging each other in the central transverse reload. The amount of the deflections determines 40 giun ci the seid wheels, the ends cf the engaging how much mis-matching of the teeth is desirable. Sides ci the teeth devinting from each other by At all times the tooth load should not be allowed en amount renin-,ing from the difference in the to become concentrated at a local area in one radius of curvature to provide for e, rccking enend of the teeth as this causes chipping of the gegement to ececmmcdete limited miei-,ive movecorners and rapid ailllre5 45 ments of the axes or the gear and pinion wheels.

In Figure 4, I illustrate the manner 0f Produc- 2. A gear wheel and a pinion wheel construcing curved helical gears and this is accomplished tion comprising' e geinwheei having en exis by lowering the plane of the blank o below and having a plurality of curved teeth each havthe axial Center 0f the cutting head, S0 ing a generated mvolute Drome. the spaces bethe revolving 0f the cutters, as illustrated tween the 'being the same from Que Side by the dash-nddot circle passes through the of the wheel to the other and the Sides 0f the blank I4 et en angle t0 the face of the hie-hkspaces being arcs of circles having a common On a curved tooth helical. a line tangent to the center e pinion wneei having en exis subsi-,en tooth in the center of its face makes an angle tieiiy nei-enel tc the exis of the geef wheel and the axial center Of the Wheel' Whereas m having'a of similar curved teeth each Figure 3 on a Curved tooth Spur o' line tehgeht having a generated involute profile adapted to to the curved tooth at the center of its face is mesh with the curved teeth i the gear wheel parallel to the axial center of the wheel. The the spaces between the teeth of the pinion wheei helical angle oeh he Varied hy changing the hsbeing the same from one side of the wheel to tance between the median plane 42 of the blank e0 the other and the sides ci the spaces being arcs and the axial eehtel u' In looth the Curved of circles having a common center, the tooth spur gear and the curved helical gear, the conspace between a.diecent teeth of the gear Wheel VeX Side 0f the tooth Space of one wheel and and of the pinion wheel defined by a convex and the concave Side 0f the tooth Space 0f the other a concave side, each said side being curved about wheel engage each other for a transverse distance the same generating center lying substantially in less than the width o! either the gear wheel or the center plane of the wheels and being genthe pinion wheel, with the ends of the teeth erated with dlierent radii of curvature, the rarelieved to provide for the rocking engagement. dius of curvature of the convex side of the tooth In both the spur and the helical type or curved space being smaller than the radius of curvature gear, the convex and the concave side of the 'l0-ol the concave side by an amount substantially tooth spaces are generated about the same genequal to the tooth space between adjacent teeth. erating center 34 with diierent radii of curvaand the convex side oi the toothv space of one tures. In the case of the curved spur gear, the wheel and the concave side of the tooth space generating center 34 lies within the median plane of the other wheel engaging each other in the of the wheel blank, whereas in thecase of the central transverse region ofthe saidwheels, the

ends of the engaging sides of the teeth deviating from each other by an amount resulting from the diiference in the radius of curvature to provide for a rocking engagement to accommodate limited relative movements of the axes of the gear and pinion wheels.

3. A gear wheel and a pinion wheel construction comprising, a gear wheel having an axis and having a plurality of curved teeth each having a generated involute prole, thev spaces between the teeth being the same from one side of the wheel to the other and the sides of the spaces being arcs of circles having a common center, a pinion Wheel having an axis substantially parallel to 'the axis ofl the gear wheel and having a plurality of similar curved teeth each having a generated involute proille adapted to mesh with the curved .teeth oi' the gear Wheel, the spaces between the teeth of the pinion wheel being the same from one side of the wheel to the other and the sides of the spaces beingarcs of circles having a commoncenter, the tooth space between adjacent teeth of the gear wheel and of the pinion wheel deilned-by a convex and a, concave side, each said side being curved about the same generating center lying outside the center plane of the wheels and being generated with diierent radii of curvature, the radius of curvature of the convex side oi' the tooth space being smaller than the radius of curvature of the' concave side by an amount substantially equal to the tooth space between adjacent teeth, and the convex side of the tooth space of one wheel and the concave side of the tooth space of .the other wheel engaging each other in the central transverse region of the said wheels, the ends oi.' the engaging sides of the teeth deviating from each other by an amount resulting from the difference cave side, each in the radius oi' curvature to provide for a rocking engagement to accommodate limited relative movements of the axes of the gear and pinion wheels.

4. A gear wheel and a pinion wheel construction comprising, a gear wheel having a plurality of curved teeth each having a generated involute prole, the spaces between the teeth being the same from one side oi' the wheel to the other and the sides of thespaces being arcs of circles having a common center, a pinion wheel having a plurality of similar curved teeth each having a generated involute prole adapted to mesh with the curved teeth of the gear wheel, the spaces between the teeth of the pinion wheel being the same from one side of the wheel to the other and the sides oi.' the spaces being arcs of circles having a common center, the tooth space between adjacent teeth of the gear wheel and of the pinion wheel defined by a convex and a. consaid side being curved about the same generating center with different radii of curvature, the radius of curvature oi. the convex side of the tooth space being smaller than the radius of curvature of the concave side by an amount substantially equal to the tooth space between adjacent teeth. and the convex side of the tooth space of one wheel and the concave side of the tooth space of the other wheel engaging each other in the central transverse region of the said wheels,the ends of the engaging sides of the teeth deviating from each other by an amount resulting from the difference in the radius of curvature to provide for a rocking engagement to accommodate limited relative movements of the gear and pinion wheels.

FRANCIS H. BOOR. 

